drivers: spi_nrfx_spim: Fix limiting of SPIM frequency on nRF5340

According to the nRF5340 PS, SPIM4 only supports 32 Mbps when
the application core is running at 128 MHz. This patch adds
the corresponding check.

Signed-off-by: Andrzej Głąbek <[email protected]>

Author: anangl

drivers/spi/spi_nrfx_spim.c

@@ -6,6 +6,7 @@
 
 #include <drivers/spi.h>
 #include <nrfx_spim.h>
+#include <hal/nrf_clock.h>
 #include <string.h>
 
 #define LOG_DOMAIN "spi_nrfx_spim"
@@ -104,9 +105,11 @@ static inline nrf_spim_bit_order_t get_nrf_spim_bit_order(uint16_t operation)
 static int configure(const struct device *dev,
 		     const struct spi_config *spi_cfg)
 {
+	const struct spi_nrfx_config *dev_config = get_dev_config(dev);
 	struct spi_context *ctx = &get_dev_data(dev)->ctx;
-	const nrfx_spim_t *spim = &get_dev_config(dev)->spim;
-	nrf_spim_frequency_t freq;
+	const nrfx_spim_t *spim = &dev_config->spim;
+	uint32_t max_freq = dev_config->max_freq;
+	nrf_spim_frequency_t spim_frequency;
 
 	if (spi_context_configured(ctx, spi_cfg)) {
 		/* Already configured. No need to do it again. */
@@ -143,14 +146,24 @@ static int configure(const struct device *dev,
 	ctx->config = spi_cfg;
 	spi_context_cs_configure(ctx);
 
+#if defined(CONFIG_SOC_NRF5340_CPUAPP)
+	/* On nRF5340, the 32 Mbps speed is supported by the application core
+	 * when it is running at 128 MHz (see the Timing specifications section
+	 * in the nRF5340 PS).
+	 */
+	if (max_freq > 16000000 &&
+	    nrf_clock_hfclk_div_get(NRF_CLOCK) != NRF_CLOCK_HFCLK_DIV_1) {
+		max_freq = 16000000;
+	}
+#endif
 	/* Limit the frequency to that supported by the SPIM instance */
-	freq = get_nrf_spim_frequency(MIN(spi_cfg->frequency,
-					  get_dev_config(dev)->max_freq));
+	spim_frequency = get_nrf_spim_frequency(MIN(spi_cfg->frequency,
+						    max_freq));
 
 	nrf_spim_configure(spim->p_reg,
 			   get_nrf_spim_mode(spi_cfg->operation),
 			   get_nrf_spim_bit_order(spi_cfg->operation));
-	nrf_spim_frequency_set(spim->p_reg, freq);
+	nrf_spim_frequency_set(spim->p_reg, spim_frequency);
 
 	return 0;
 }